Source code for colour.models.cie_lab

# -*- coding: utf-8 -*-
"""
CIE L*a*b* Colourspace
======================

Defines the *CIE L\\*a\\*b\\** colourspace transformations:

-   :func:`colour.XYZ_to_Lab`
-   :func:`colour.Lab_to_XYZ`
-   :func:`colour.Lab_to_LCHab`
-   :func:`colour.LCHab_to_Lab`

References
----------
-   :cite:`CIETC1-482004m` : CIE TC 1-48. (2004). CIE 1976 uniform colour
    spaces. In CIE 015:2004 Colorimetry, 3rd Edition (p. 24).
    ISBN:978-3-901906-33-6
"""

from __future__ import division, unicode_literals

from colour.colorimetry import (ILLUMINANTS,
                                intermediate_lightness_function_CIE1976,
                                intermediate_luminance_function_CIE1976)
from colour.models import xy_to_xyY, xyY_to_XYZ, Jab_to_JCh, JCh_to_Jab
from colour.utilities import (from_range_1, from_range_100, to_domain_1,
                              to_domain_100, tsplit, tstack)

__author__ = 'Colour Developers'
__copyright__ = 'Copyright (C) 2013-2020 - Colour Developers'
__license__ = 'New BSD License - https://opensource.org/licenses/BSD-3-Clause'
__maintainer__ = 'Colour Developers'
__email__ = 'colour-developers@colour-science.org'
__status__ = 'Production'

__all__ = ['XYZ_to_Lab', 'Lab_to_XYZ', 'Lab_to_LCHab', 'LCHab_to_Lab']


[docs]def XYZ_to_Lab( XYZ, illuminant=ILLUMINANTS['CIE 1931 2 Degree Standard Observer']['D65']): """ Converts from *CIE XYZ* tristimulus values to *CIE L\\*a\\*b\\** colourspace. Parameters ---------- XYZ : array_like *CIE XYZ* tristimulus values. illuminant : array_like, optional Reference *illuminant* *CIE xy* chromaticity coordinates or *CIE xyY* colourspace array. Returns ------- ndarray *CIE L\\*a\\*b\\** colourspace array. Notes ----- +----------------+-----------------------+-----------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +================+=======================+=================+ | ``XYZ`` | [0, 1] | [0, 1] | +----------------+-----------------------+-----------------+ | ``illuminant`` | [0, 1] | [0, 1] | +----------------+-----------------------+-----------------+ +----------------+-----------------------+-----------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +================+=======================+=================+ | ``Lab`` | ``L`` : [0, 100] | ``L`` : [0, 1] | | | | | | | ``a`` : [-100, 100] | ``a`` : [-1, 1] | | | | | | | ``b`` : [-100, 100] | ``b`` : [-1, 1] | +----------------+-----------------------+-----------------+ References ---------- :cite:`CIETC1-482004m` Examples -------- >>> import numpy as np >>> XYZ = np.array([0.20654008, 0.12197225, 0.05136952]) >>> XYZ_to_Lab(XYZ) # doctest: +ELLIPSIS array([ 41.5278752..., 52.6385830..., 26.9231792...]) """ X, Y, Z = tsplit(to_domain_1(XYZ)) X_n, Y_n, Z_n = tsplit(xyY_to_XYZ(xy_to_xyY(illuminant))) f_X_X_n = intermediate_lightness_function_CIE1976(X, X_n) f_Y_Y_n = intermediate_lightness_function_CIE1976(Y, Y_n) f_Z_Z_n = intermediate_lightness_function_CIE1976(Z, Z_n) L = 116 * f_Y_Y_n - 16 a = 500 * (f_X_X_n - f_Y_Y_n) b = 200 * (f_Y_Y_n - f_Z_Z_n) Lab = tstack([L, a, b]) return from_range_100(Lab)
[docs]def Lab_to_XYZ( Lab, illuminant=ILLUMINANTS['CIE 1931 2 Degree Standard Observer']['D65']): """ Converts from *CIE L\\*a\\*b\\** colourspace to *CIE XYZ* tristimulus values. Parameters ---------- Lab : array_like *CIE L\\*a\\*b\\** colourspace array. illuminant : array_like, optional Reference *illuminant* *CIE xy* chromaticity coordinates or *CIE xyY* colourspace array. Returns ------- ndarray *CIE XYZ* tristimulus values. Notes ----- +----------------+-----------------------+-----------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +================+=======================+=================+ | ``Lab`` | ``L`` : [0, 100] | ``L`` : [0, 1] | | | | | | | ``a`` : [-100, 100] | ``a`` : [-1, 1] | | | | | | | ``b`` : [-100, 100] | ``b`` : [-1, 1] | +----------------+-----------------------+-----------------+ | ``illuminant`` | [0, 1] | [0, 1] | +----------------+-----------------------+-----------------+ +----------------+-----------------------+-----------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +================+=======================+=================+ | ``XYZ`` | [0, 1] | [0, 1] | +----------------+-----------------------+-----------------+ References ---------- :cite:`CIETC1-482004m` Examples -------- >>> import numpy as np >>> Lab = np.array([41.52787529, 52.63858304, 26.92317922]) >>> Lab_to_XYZ(Lab) # doctest: +ELLIPSIS array([ 0.2065400..., 0.1219722..., 0.0513695...]) """ L, a, b = tsplit(to_domain_100(Lab)) X_n, Y_n, Z_n = tsplit(xyY_to_XYZ(xy_to_xyY(illuminant))) f_Y_Y_n = (L + 16) / 116 f_X_X_n = a / 500 + f_Y_Y_n f_Z_Z_n = f_Y_Y_n - b / 200 X = intermediate_luminance_function_CIE1976(f_X_X_n, X_n) Y = intermediate_luminance_function_CIE1976(f_Y_Y_n, Y_n) Z = intermediate_luminance_function_CIE1976(f_Z_Z_n, Z_n) XYZ = tstack([X, Y, Z]) return from_range_1(XYZ)
[docs]def Lab_to_LCHab(Lab): """ Converts from *CIE L\\*a\\*b\\** colourspace to *CIE L\\*C\\*Hab* colourspace. Parameters ---------- Lab : array_like *CIE L\\*a\\*b\\** colourspace array. Returns ------- ndarray *CIE L\\*C\\*Hab* colourspace array. Notes ----- +------------+-----------------------+-----------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +============+=======================+=================+ | ``Lab`` | ``L`` : [0, 100] | ``L`` : [0, 1] | | | | | | | ``a`` : [-100, 100] | ``a`` : [-1, 1] | | | | | | | ``b`` : [-100, 100] | ``b`` : [-1, 1] | +------------+-----------------------+-----------------+ +------------+-----------------------+------------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +============+=======================+==================+ | ``LCHab`` | ``L`` : [0, 100] | ``L`` : [0, 1] | | | | | | | ``C`` : [0, 100] | ``C`` : [0, 1] | | | | | | | ``Hab`` : [0, 360] | ``Hab`` : [0, 1] | +------------+-----------------------+------------------+ References ---------- :cite:`CIETC1-482004m` Examples -------- >>> import numpy as np >>> Lab = np.array([41.52787529, 52.63858304, 26.92317922]) >>> Lab_to_LCHab(Lab) # doctest: +ELLIPSIS array([ 41.5278752..., 59.1242590..., 27.0884878...]) """ return Jab_to_JCh(Lab)
[docs]def LCHab_to_Lab(LCHab): """ Converts from *CIE L\\*C\\*Hab* colourspace to *CIE L\\*a\\*b\\** colourspace. Parameters ---------- LCHab : array_like *CIE L\\*C\\*Hab* colourspace array. Returns ------- ndarray *CIE L\\*a\\*b\\** colourspace array. Notes ----- +-------------+-----------------------+------------------+ | **Domain** | **Scale - Reference** | **Scale - 1** | +=============+=======================+==================+ | ``LCHab`` | ``L`` : [0, 100] | ``L`` : [0, 1] | | | | | | | ``C`` : [0, 100] | ``C`` : [0, 1] | | | | | | | ``Hab`` : [0, 360] | ``Hab`` : [0, 1] | +-------------+-----------------------+------------------+ +-------------+-----------------------+-----------------+ | **Range** | **Scale - Reference** | **Scale - 1** | +=============+=======================+=================+ | ``Lab`` | ``L`` : [0, 100] | ``L`` : [0, 1] | | | | | | | ``a`` : [-100, 100] | ``a`` : [-1, 1] | | | | | | | ``b`` : [-100, 100] | ``b`` : [-1, 1] | +-------------+-----------------------+-----------------+ References ---------- :cite:`CIETC1-482004m` Examples -------- >>> import numpy as np >>> LCHab = np.array([41.52787529, 59.12425901, 27.08848784]) >>> LCHab_to_Lab(LCHab) # doctest: +ELLIPSIS array([ 41.5278752..., 52.6385830..., 26.9231792...]) """ return JCh_to_Jab(LCHab)